1. Field of the Invention
The present invention relates in general to a microwave oven and a method of controlling the same, and more particularly, to a microwave oven and a method of controlling the same, which is able to prevent an application of a lower voltage than an allowable lower limit voltage.
2. Description of the Related Art
Conventionally, a microwave oven is operated in the following process. An alternating current (AC) power supplied from a power supply part is applied to a primary coil of a high voltage transformer, and a high voltage is then generated in a secondary coil thereof. The high voltage generated in the secondary coil of the high voltage transformer is used to heat a cathode filament provided in a magnetron, the magnetron is then oscillated by the applied high voltage, and a very high frequency energy is then radiated. The very high frequency energy is transformed into heat energy when it encounters with water or water-containing objects (for example, foodstuff, etc.) within a closed space, and the heat energy is used for cooking.
FIG. 5 is a schematic block diagram showing a control process of a conventional microwave oven. As illustrated therein, the conventional microwave oven is comprised of a power supply part 101 supplying an alternating current (AC) power, a magnetron 109 generating electromagnetic waves with a high voltage generated from a high voltage transformer 107, a rectifier and smoother part 103 rectifying and smoothing the AC power, an inverter part 105 converting a direct current (DC) power from the rectifier and smoother part 103 into an AC power of a high frequency, the high voltage transformer 107 generating the high voltage with the AC power supplied from the power supply part 101 through the rectifier and smoother part 103 and the inverter part 105, a signal generator part 127 generating a control signal, and an inverter controller part 115 interposed between the inverter part 105 and the signal generator part 107.
The inverter controller part 115 includes a digital/analog (D/A) converter part 125 converting the control signal generated from the signal generator part 127 into an analog signal and applying the converted control signal to a resonance detector part 121, an output control part 119 controlling a frequency of the control signal detected by the resonance detector part 121 to output it, and an oscillator part 117 changing a cycle of the control signal outputted from the output control part 119 according to the frequency thereof and inputting the changed cycle into the inverter part 105. The inverter controller part 115 further includes an on-off starter part 123 controlling on-off operations and a soft start operation of the oscillator part 117 according to the control signal generated from the signal generator part 127.
However, where the voltage of the AC power inputted from the power supply part is lower than an allowable lower limit voltage, the high voltage generated in the secondary coil of the high voltage transformer is relatively lowered. Accordingly, an efficiency of generating the electromagnetic waves in the magnetron is lowered, and the cooking time is relatively lengthened.
In addition, where a value of the current smoothed through the rectifier and smoother part exceeds a predetermined allowable current value, the circuit is overloaded, thereby being liable to lower a stability of the overall circuitry.
Accordingly, the present invention has been made keeping in mind the above-shortcoming, and an object of the present invention is to provide a microwave oven and a method of controlling the same, which is able to interrupt a power having a voltage lower than an allowable voltage from being inputted, and increase an efficiency of outputting a frequency from the magnetron.
This and other objects of the present invention may be accomplished by the provision of a microwave oven including a magnetron, a power supply part supplying an AC power and a high voltage transformer generating a high voltage with the AC power from the power supply part, comprising a power controller part interrupting the power supply to the magnetron where it is determined that the voltage of the power supplied from the power supply part is lower than a predetermined allowable lower limit voltage.
The microwave oven further comprises a rectifier and smoother part rectifying and smoothing the AC power; an inverter part converting a DC power from the rectifier and smoother part into an AC power having a high voltage; and an inverter controller part interrupting the power supply to the magnetron where it is determined that the voltage of the power supplied from the power supply part is lower than the predetermined allowable lower limit voltage.
Preferably, the power controller part determines whether the current value of the power inputted into the high voltage transformer exceeds a predetermined allowable current value, interrupts the power from the power supply part being inputted into the magnetron where the current value is in excess of the allowable current value, and resumes an operation of the magnetron after a predetermined period of time for recess has passed.
The power controller part interrupts the power supply to the magnetron where the voltage of the power supplied from the power supply part exceeds a predetermined allowable upper limit voltage, thereby enhancing a stability of a circuitry.
Preferably, the power controller part further includes a comparator comparing the voltage of the power supplied from the power supply part with the predetermined allowable lower limit voltage to determine whether the voltage of the supplied power is lower that the allowable lower limit voltage.
According to another aspect of the present invention, this and other objects of the present invention may also be accomplished by the provision of a method of controlling a microwave oven including a magnetron, a power supply part supplying an AC power and a high voltage transformer generating a high voltage with the AC power from the power supply part, comprising the steps of determining whether the voltage of the power supplied from the power supply part is lower than a predetermined allowable lower limit voltage; and interrupting the power supply to be applied to the magnetron where it is determined that the voltage of the power supplied from the power supply part is lower than the predetermined allowable lower limit voltage.
Effectively, the method further comprises the steps of determining whether the voltage of the power supplied from the power supply part exceeds a predetermined allowable upper limit voltage; and interrupting the power supply to be applied to the magnetron where it is determined that the voltage of the power supplied from the power supply part exceeds the predetermined allowable upper limit voltage.
The method further comprises the steps of determining whether the current value of the power inputted into the high voltage transformer exceeds the predetermined allowable current value; and interrupting the power supply to the magnetron where it is determined that the current value of the power is in excess of the allowable current value, and resuming an operation of the magnetron after a predetermined period of time for recess has passed, thereby enhancing a stability of a circuitry.
Preferably, a comparator compares the voltage of the power supply with the allowable voltage determines whether the voltage of the power supply is lower than the predetermined allowable voltage.